Depends on which PDF viewer you use. For Adobe Reader you are out of luck, since LEd doesn't have DDE to talk to AR. You could go around this by calling a command line DDE tool from LEd, but the last time I checked none of such tools I could find actually worked.

If you are OK with using an alternative viewer, such as PDF-XChange, then this thread might be of interest. An even simpler solution is to use a no-file-locking viewer such as SumatraPDF or TeXwokrs (a TeX editor with an integrated PDF viewer; bundled with the latest versions of TeX Live and MiKTeX).